Module: NumRu

Defined in:

lib/numru/misc/keywordopt.rb,
lib/numru/misc/misc.rb,
lib/numru/misc/emath.rb,
lib/numru/misc/md_iterators.rb

Overview

module NumRu::Misc::MD_Iterators

A Mixin. To be included in a class with multi-dimension indexing support (such as NArray).

Index

• ((<each_subary_at_dims>))

• ((<each_subary_at_dims_with_index>))

Methods

—each_subary_at_dims( *dims )

Iterator for each sub-array (not each element) specified by dimensions.

ARGUMENT
* ((|dims|)) (integers) : specifies subsets at dimensions 
  specified here with the beginning-to-end selection. 
  For example, [0, 1] to specify the first 2 dimensions 
  (subsets will be 2D then), and [2] to specify the 3rd 
  dimension (subsets will be 1D). Duplication has no effect, 
  so [0,0] and [0] are the same. Also, its order has no effect.
  See EXAMPLE below for more.

RETURN VALUE
* self

POSSIBLE EXCEPTIONS
* exception is raised if ( dims.min<0 || dims.max>=self.rank ).

EXAMPLE

* Suppose that you want to do something with 2D sub-arrays in a
  multi-dimension NArray. First, you include this module as follows:

    require "narray"
    class NArray
       include NumRu::Misc::MD_Iterators
    end

  And prepare the array if you have not (here, it is 4D):

    na = NArray.int(10,2,5,2).indgen!

  Then you do the job like this:

    na.each_subary_at_dims(0,2){ |sub|
      ...  # do whatever with sub
    }

  This is equivalent to the following:

    (0...na.shape[3]).each{|j|
      (0...na.shape[1]).each{|i|
        sub = na[0..-1, i, 0..-1, j]
        ...  # do whatever with sub
      }
    }

  Note that the loop must be nested 3 times when (('na')) is a 5D array,
  if the latter approach is used. On the other hand, it will still 
  require the same single loop with the former.

—each_subary_at_dims_with_index( *dims )

Like ((<each_subary_at_dims>)) but the block takes two arguments:
subset and the subset specifier (index).

EXAMPLE
* Suppose the example above in ((<each_subary_at_dims>)) (EXAMPLE).
  And suppose that you want to overwrite (('na')) with the result
  you get. You can do it like this:

    na.each_subary_at_dims_with_index(0,2){ |sub,idx|
      result = (sub + 10) / 2
      na[*idx] = result
    }

  Here, (('idx')) is an Array to be fed in the []= or [] methods
  with asterisk (ungrouping).

Defined Under Namespace

Modules: Misc